Alpha-numeric print system using three printing wheels

ABSTRACT

A printing system is described having three continuously rotating print wheels slidably mounted adjoining each other on a splined shaft. A record sheet, which may be a card or a sheet of paper is mounted adjacent the peripheries of the wheels and an electromagnetic hammer is mounted on the other side of the record sheet. The printing operation includes the actuation of the hammer in timed relationship to the position of the wheels. The wheels are shifted together by a single yoke to move a desired wheel into printing position. Three wheels are used in order to include all the alphabet characters, all the numerals from 0 to 9, and various other punctuation marks.

[4 1 Jan. 25, 1972 [54] ALPHA-NUMERIC PRINT SYSTEM USING THREE PRINTING WHEELS [72] Inventors: Arnold M. Wolf, Brooklyn; John G.

Richter, Yonkers, both of NY.

Electrospace Corporation, Glen Cove, NY.

22 Filed: Nov. 12,1969

211 Appl.No.: 875,794

[73] Assignee:

[55 MM a.

1,936,656 11/1933 Bell ..178/34 Primary Examiner-Kathleen H. Claffy Assistant Examiner-Thomas W. Brown Attorney-Albert F. Kronman [5 7 1 ABSTRACT A printing system is described having three continuously rotating print wheels slidably mounted adjoining each other on a splined shaft. A record sheet, which may be a card or a sheet of paper is mounted adjacent the peripheries of the wheels and an electromagnetic hammer is mounted on the other side of the record sheet. The printing operation includes the actuation of the hammer in timed relationship to the position of the wheels. The wheels are shifted together by a single yoke to move a desired wheel into printing position. Three wheels are used in order to include all the alphabet characters, all the numerals from 0 to 9, and various other punctuation marks.

7 (Zlaims, 16 Drawing Figures ALPHA-NUMERIC PRINT SYSTEM USING THREE PRINTING WHEELS BACKGROUND OF THE INVENTION The present invention relates to a print system which can be used in connection with a computer system for a readout means. In order to qualify for such an application, the print system must be fast, dependable, and adaptable to the output circuit of the computer. Many print systems have been developed for similar uses, some including a modified typewriter mechanism which is cumbersome and occupies too much space. The multiple-sectored wheel used in punched card systems is too slow and is not well adapted to serial com puter operation since all characters are printed at the same time. The old ticker tape printer was slow and the single wheel had to be stopped in position and then moved laterally to print. The present invention employs three small wheels which rotate all the time the system is in operation. A total of 45 printing positions are available for characters and the system occupies a small space.

A feature of the present invention is a plural-type wheel combination which is shiftable for printing any character on.

any wheel at a desired position.

Another feature of the invention is a timed relationship between the position of the wheels and a timing matrix which selects the character to be printed.

Still another feature of the invention is a control means for shifting the record sheet to a new printing position and to a new line.

For a better understanding of the present invention, together with other details and features thereof, reference is made to the following description taken in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE FIGURES FIG. 1 is schematic diagram of connections showing the input circuit, selection filters, gate circuits, and storage multivibrators for generating timed control pulses for operating the print system.

FIG. 2 is a schematic diagram of connections of the diode matrix, the actuating multivibrators, and the optical transducers which control them.

FIG. 3 is a diagram of one of the storage multivibrators which may be used in the circuit shown in FIG. 1.

FIG. 4 is a circuit diagram of matrix multivibrator which successively changes the conductive characteristics of the diode matrix shown in FIG. 2.

FIG. 5 is a circuit diagram showing the printing wheels, the one-revolution clutches and four control circuits in block.

FIG. 6 is a diagram of connections of an alternate form of diode matrix which may be used instead of the matrix shown in FIG. 2.

FIG. 7 is a cross-sectional view of a light control wheel used with the matrix shown in FIG. 6.

FIG. 8 is a diagram of connections showing the photosensitive circuit which may be used in connection with the optical wheel shown in FIGS. 6 and 7.

FIG. 9 is a plan view of the optical wheel used in connection with the circuit shown in FIG. 2.

FIG. 10 is a diagram of connections of the end of message circuit, shown in block in FIG. 5.

FIG. 11 is a diagram of connections of the space circuit shown in block in FIG. 5.

FIG. 12 is a detailed circuit diagram of an AND circuit having two inputs.

FIG. 13 is a circuit diagram of a filter circuit which may be used as indicated in FIG. 1.

FIG. 14 is a diagram of a print control circuit shown in block in FIG. I.

FIG. 15 is a diagram of an OR gate as used in FIG. 1.

FIG. 16 is a diagram of an AND" circuit having three input terminals. This circuit is shown in block in FIG. 1.

FIGS. 1, 2, and 5, when placed side by side form a complete wiring diagram of the entire print system.

GENERAL DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIG. 1, the print circuit includes a pair of input terminals 20 for connection with a signalling circuit (not shown) which applies two or three signal frequency waves to the print circuit to print a desired character. The signal waves are amplified by a combined amplifier and band-pass filter 21 which isolates the print circuit and eliminates most of the line noise. The output of the amplifier-filter 21 is applied to ID filter circuits 22-1 through 22-10. These filter circuits each contain a sharply tuned filter and a buffer amplifier. Many types of such circuits can be used in this position to separate the combined frequency waves received from amplifier 21. One such circuit is shown in detail in FIG. 13 where an integrated amplifier 23 is employed in conjunction with a double T filter 24 coupled between the amplifier 23 and an output amplifier stage 25 which includes a transistor 26. The amplifier 23 is available commercially as PA 230, sold by the General Electric Co. Intermediate the amplifier 23 and transistor 26 is a clamping diode 27 and a clipper section including another diode 28 and resistors 30 and 31. There are many variations of these components and the invention is not dependent upon the details of construction as shown.

Each filter circuit 22 has its output connected to a plurality of AND-gates 32 which can be opened to transmit an output pulse only when it receives two input pulses. FIG. 12 shows a typical AND gate having input terminals 33 and 34 and a single output terminal 35. When either one (or none) of the input terminals receives a negative input pulse, there is no output signal because the other diode branch, either through diode 36 or diode 37, maintainsthe output terminal 35 at substantially ground potential. When both input terminals receive negative pulses, the junction point 38 is reduced in potential and a negative pulse is applied through diode 40 to the output terminal 35. This AND circuit has been selected because its operation may be controlled by a third common circuit 41 connected in series with resistor 42. Conductor 41 is connected to control circuit 43 whose function will be described later.

The AND gates are each connected respectively to a storage multivibrator 44 which stores the signal pulse translated by the gates 32 until the end of a printing cycle. These storage units are necessary because the signal inputs to the gate circuits may be of short duration and printing can be done only if the printing wheels are turned to the desired character. The signal pulse must remain on the output conductors until a printing cycle has been completed.

As shown in FIG. 1 eight of the filter circuits are used to operate gates to select the desired symbol to be printed. The ninth and 10th filter circuits 229 and 22-10 are for selecting the proper wheel. If the ninth filter circuit receives a frequency which corresponds to the filter frequency, a pulse is sent over conductor 45 to storage multivibrator 44-19 which is triggered and applies a pulse to amplifier 46 which applies an operating voltageon conductor 47. The purpose of this voltage is to send current through a magnetic winding 50 (see FIG. 5) and move an armature 51 so that a printing wheel 52 may be shifted into printing position and one of the characters on its periphery make contact with the printing hammer 53 to record a letter, a number, or other mark. If the signal voltage from the storage circuit is strong enough to operate magnet 50, amplifier 46 may be omitted. Amplifiers 46 and 54 have been shown in FIG. 1 in order to insure positive and quick action.

In a similar manner, the last filter circuit 2210 is activated by a signal having a frequency corresponding to the filter frequency and the first printing wheel 55 is moved into printing position. The signal from filter-amplifier 22-10 is sent to amplifier 56, then to storage circuit 4420, amplifier 57 and conductor 58 to magnet 62.

As indicated in FIG. 1, the first I5 gates 32 and the first l5 storage multivibrators are used to select and print 45 charac ters. While the printing operations require the shifting of the prim wheels for 30 of the 45 symbols, there is no other type of mechanical operation required except to space the card tray vertically. However, the mechanism does perform the following: (I) move the card tray up one line space when NEXT LINE" is requested; (2) print an asterisk at the end of a message EOM and normalize all circuits; (3) space the printing assembly one space between words when a SPACE" is requested; and (4) inhibit the hammer operation during a space operation. These four operations are performed by selective signalling with coded frequencies using gates 32-16, 32-17, and 32-18; also filter circuits 22-9 and 22-10.

A NEXT LINE signal is generated by applying two frequency waves to gate 32-16 from filters 22-3 and 22-7. The gate applies the signal to the storage multivibrator and then to conductor 60 and to the End of Message Circuit" 61 (FIGS. 5, and The detailed operation of this complete circuit and the Next Line operation will be discussed later. The Next Line storage circuit 44-16 receives an activating pulse each time filter circuits 22-3 and 22-7 transmit pulses. Circuits 44-17 and 44-18 are activated only when they receive operating pulses from gates 32-17 and 32-18, each of which require three input pulses before producing an output pulse. Gate 32-17 is connected to filters 22-3, 22-7, and 22-9 while gate 32-18 is connected to filters 22-3, 22-7, and 22-10. It is obvious that gate 32-16 would be activated each time gates 32-17 and 32-18 are activated if some inhibiting feature were not provided. The inhibitor circuit includes an OR"-circuit 70 which has input connections to amplifiers 54 and 56. The output of the 011" circuit is connected by means of conductor 71 to an inhibit terminal on the storage multivibrator 44-16. This circuit is shown in detail in FIG. 3.

Gate 32-17, as mentioned above, sends an actuating pulse to storage circuit 44-17 each time the gate receives three input pulses. The detailed circuit diagram of the triple gate is shown in FIG. 16. One output from storage circuit 44-17 is applied over conductor 72 to the End of Message circuit 61 shown in block in FIG. 5 and in detail in FIG. 10. The operation of this circuit will be discussed later.

In order to show when the message is complete, a special symbol, an asterisk is printed on the card. To print this symbol, a pulse is sent from circuit 44-17 through an OR- gate 74, then over conductor 75 to the diode matrix for timing to synchronize the hammer operation with the print wheel position.

When a space is called for, gate 32-18 is activated by pulses from three filters 22-3, 22-7, and 22-10. Storage multivibrator 44-18 is triggered and operating pulses are applied to conductors 76 and 77. Conductor 76 sends an operating pulse through OR-circuit 74 and conductor 75 to print an asterisk but, at the same time, a control pulse is sent over conductor 77 to the print control circuit 78 to disable it by short circuiting the input terminals and thereby cutting off current to the hammer winding 80. This action produces a space operation because no printing action is permitted.

Referring now to FIG. 5, the three printing wheels 52, 55, and 63 are all mounted as a single unit on a splined shaft 64. The printing wheels are movable, as a unit, along the shaft by means of a grooved wheel 65 and a U-shaped yoke 66. The yoke 66 is secured to a main lever 67 which is pivoted to a portion of the printing assembly 68 and is coupled to armature 51 by a bar 69. The lever 67 is resiliently positioned at a central point by two small levers 81 and 82, held together by a spring 83. When the lever 67 is in the central position, as shown in the figure, the two small levers limit against a stud 84, secured to the baseplate 85. When armature 51 moves the main lever 67 to the right or left, one of the small levers 81, 82, is moved with it stretching spring 83. Armature 51 is limited in its movement by two stops 86, also secured to the baseplate 85.

The printing assembly also includes a printing means which comprises the magnet winding 80, a pivoted bar 87 and a hammer face 53. The entire printing assembly is mounted on a baseplate 85 which is movable along a track (not shown) by means of a tension spring 88, an escapement rack 90, and an escapement pawl 91. The pawl 91 is operated by an electromagnet 92 which activates an armature 93 and pulls a cord 94 to move the pawl each time a blank space is desired or a character is printed. Other details of the printing means will be disclosed later.

DIODE MATRIX Synchronism between the decoding circuits and the printing wheels is provided by a diode matrix and a series of four multivibrators 95, 96, 97, and 98, shown in FIG. 2. The details of the multivibrator circuits are shown in FIG. 4. The diode matrix includes 16 horizontal conductors connected to storage multivibrators 44 (FIG. 1) and 32 diodes which connect selected horizontal conductors to eight vertical conductors. The vertical conductors are coupled through diodes to the matrix multivibrators for the application of operating voltages. The horizontal conductors are terminated by a common conductor 106 each in series with a blocking diode 107. The common conductor 106 is connected to a print-timing circuit 259 in series with a blocking capacitor 108. The output of the timing circuit 259 is connected by conductor 110 to the print control circuit 78, shown in detail in FIG. 14. All the horizontal conductors are provided with a bias voltage of +l 3 volts, derived from battery 111 and distributed to each horizontal conductor by conductor 112 in series with resistors 113.

The four matrix multivibrators 98, 95, 96, and 97, are of similar construction (see FIG. 4). These circuits are connected in cascade in a manner similar to a binary counting circuit with a single input terminal 114. Operating pulses to operate these multivibrators are applied over conductor 115 from a transistor 116 acting as an amplifier for a transducer 117. The transducer 117 transforms light pulses into electrical pulses which are then amplified by transistor 116. The light pulses are received from a lamp 118 shining through a series of holes 119 out in a rotatable flat wheel 120 turned by shaft 64 and an electric motor 121. Shaft 64 also supports printing wheels 52, 55, 63. Wheel 120 (see FIG. 9) contains 16 holes, 15 of which are disposed so as to transmit light from lamp 118 and one hole 122, closer to the center of rotation for passing light from a second lamp 123 to activate a second photosensitive transducer 124. Transducer 124 is coupled to amplifier transistor 125 which is connected to conductor 126 and all of the reset terminals 127 on the matrix multivibrators.

Light flashes from lamp 118 are transformed into electrical pulses by transducer 117, amplified by transistor 116, and then a negative pulse is applied to input terminal 114 over conductor 115 to transfer conductance from the right-hand transistor 95A (see FIG. 4) to the left-hand transistor 958. When a second pulse is received, conductance is transferred back to transistor 95A and, at the same time. a triggering negative pulse is sent from the output terminal 128 to the input terminal 130 of the second matrix multivibrator 96. The second multivibrator 96 is identical to the first and conductance of its transistors is transferred in a similar manner. During the second activation of multivibrator 96, a pulse is sent to the third multivibrator 97, and, as the operation progresses, after 15 actuating pulses from transistor 116, all the multivibrators are conductive on the left side. The 16th pulse, from transistor 125, over conductor 126 is applied to four reset terminals 127 and all the circuits are normalized ready for another cycle.

The above-described counting" operation applies a series of voltages to the vertical conductors in the matrix (see FIG. 2). When conductance is on the right side of any multivibrator, terminal 1 is at low voltage and terminal 0 is at high voltage (+13 volts). A low voltage applied to a vertical conductor results in conductance through any of the diodes 105 crossconnected between the vertical conductor and the connected horizontal conductor. In a complete series of 16 counts resulting from a single turn of wheel 120, there are 16 combinations of applied voltages given to the vertical conductors, thereby providing 16 voltage distributions in the matrix.

The output line 106 from the matrix is connected to a print timing circuit containing amplifiers and a monostable multivibrator which spaces the print pulse from the space pulse. The printing action comes first, then the entire printing assembly including the baseplate 85, the three windings 50, 62, and 80, and the three print wheels 52, 55, and 63, are moved one space to the right to a new printing position. The details of the print-timing circuit are shown and described in a patent application, Ser. No. 806,430, filed Mar. 12, 1969.

The operation of the matrix circuit is as follows: At the start of the operation, when all the storage multivibrators are normalized (conducting on the right side) and all their output circuits are at low voltage, no current pulses are generated as the matrix multivibrators change the voltage on the vertical conductors. All the horizontal conductors are connected through resistors 113 to a common supply line 112 and the positive terminal of battery 111. This causes a l3-volt potential drop across each resistor 113 but each horizontal conductor remains at zero voltage because the currents through the resistors 113 flow over the conductors and through the righthand conductive transistor in each of the multivibrator circuits 44 (see FIG. 3). Let it now be assumed that all the circuits have been reset by the beam of light from lamp 123 through hole 122. All four matrix multivibrators are now conducting on the right side and current flows through all the vertical conductors except the first 131 and the fifth 135. However, there is no current pulse sent through any of the diodes 107 to conductor 106 because there is sufficient current drain through at least one of the cross-connected diodes 105 to maintain all horizontal conductors at a low potential. For example, horizontal conductor 140 is connected through diode 105A to vertical conductor 137 and the 1 terminal in circuit 95 which is at low potential. Conductor 141 is connected by diode 105-8 and vertical conductor 136 to the 1 terminal in circuit 96 and horizontal conductor 142 is connected by diode l05-C and vertical conductor 138 to terminal 1 in circuit 95. All the other horizontal conductors are connected in a similar manner.

Now let it be assumed that wheel 120 moves three of its holes past lamp 118 and then permits light to shine through the fourth hole 119. The four pulses applied to the four timing multivibrator circuits have switched conduction four times leaving conduction in circuit 95 on the right side. The two output pulses from circuit 95 have switched conduction of circuit 96 twice leaving conduction also on the right side. The single pulse from circuit 96 has switched conduction of circuit 97 once, leaving it on the left side. All the timing multivibrators are the same as before except circuit 97 which has its terminal at low voltage and, its l terminal at high voltage. All the horizontal conductors are connected to low voltage except conductor 143, which has been raised in voltage because of the triggering of storage circuit 44-5 to print a 5, E, or R. The two diodes IOSD and 105-E connected between horizontal conductor 143 and vertical conductors 133 and 135 are connected to high-voltage multivibrator terminals on each of the diode terminals. There is no current drain through diodes 105-D and l-E and, as long as the positive potential is applied by timing multivibrator 97, a positive pulse is sent through diode 107-A to conductor 106, capacitor 108, the timing circuit 107, to the print control circuit which prints an E if there is no printing wheel shift.

If a third signal is received and passed by filter circuit 22-9, an additional pulse is sent to amplifier 46, over conductor 47, to winding 50 on the printing base 85. This pulse moves the printing wheel 52 into the printing position and an R" is printed. In a similar manner, a signal passed by filter circuit 22-10 moves the third wheel 55 into printing position and a 5 is printed.

CARD TRAY AND CONTROLS A card tray or holder 145 is designed to support a card or piece of paper which receives the printed symbols. It remains stationary for each line to be printed and at the end of the line a NEW LINE operation moves the card up one space. The card tray is preferably positioned adjacent to the printing wheels with the printing hammer 53 behind the card. The card tray is held in position by an escapernent rack 146, engaged by a pawl 147 and resiliently stressed by a spring 148. The pawl 147 is operated by a cord 150 which is pulled by a l-revolution clutch 151. Clutch 151 is mounted on shaft 64 and normally does not revolve. The clutch is triggered by a pivoted pawl 152 operated by a cord 153 and an armature 154 which releases the pawl 152 whenever a current pulse is applied to a magnet winding 155. When released by pawl 152, the lrevolution clutch 151 pulls the pawl 147 out of engagement with rack 146 and the spring 148 pulls the card tray up one line space.

When the card is first put intothe card tray 145, it is in its highest position. To start the action, a start button 156 is manually depressed and a cord 157 is pulled, releasing pawl 158 and permitting l-revolution clutch 160 to turn, pulling cord 161 and lowering the card tray into its printing position.

A third l-revolution clutch 162 is mounted on shaft 64 and operates to move the printing assembly base 85 the entire length of the printing area at the end of each message and at the end of each line. Clutch 162 is operated by a release pawl 163 pulled by either one of cords 164 or 165 when armatures 154 or 166 are actuated. When clutch 162 is operated, it pulls cord 167 and the entire printing can start. Armature 166 is actuated by a magnet winding 168 which receives a current pulse each time an End of Message is called for. Armature 166 also engages a second cord 170 which pulls a baseplate 171 to the left and completely disengages pawl 147 from rack 146. When this is done, the card tray moves all the way up to its highest position where the card may be removed from the tray.

The motor 121 drives shaft 64 and turns the three print wheels 52, 55, and 63. The supply line to the motor is connected in series with a pair of contacts 172 under the start button 156 and is coupled to a motor relay 173. The relay 173 includes a winding 174, a pair of holding contacts 175 connected in parallel with start contacts 172, and four other contact pairs arranged for operating indicating lamps and for supplying a 50 volt DC source of supply to lamps 118 and 123 ad jacent to the wheel 119 (FIG. 2). The End of Message circuit 61 is also coupled to one pair of contacts on the relay. Motor 121 is an alternating current motor and receives its current from a plug 176 which may be plugged into an AC source.

OPERATION OF CARD TRAY AND MOTOR As mentioned above, the system is started by placing a card in the card tray 145 and then depressing the start button 156. This action operates pawl 158, releasing the clutch 160 which turns and pulls cord 161 to lower the card tray into printing position. At the same time contacts 172 and 177 under the start button 156 are closed and contacts 178 at the side of the card tray 145 are closed by insulator strip 180. Contacts 172 start the alternating current motor 121 by completing a circuit which may be traced from the power plug 176, through main switch 181, over conductor 182, to the motor 121, then through contacts 172 under the start button 156, and back to the power plug over line 183. This circuit starts the motor 121.

When contacts 178 are closed due to the lowering of the card tray 145, a circuit is completed which may be traced from the positive terminal of a source of direct current power 184, over conductor 185, through contacts 178, to winding 174 of the relay 173, and then to ground and the other terminal of source 184. This action operates the relay, closes four pairs of contacts and opens one pair. The closure of contacts 175 completes a holding circuit which can be traced from the positive terminal of battery 184, through closed contacts 178, the relay winding 174 and back to the other side of the battery 184. This holding circuit retains the relay in its operated condition after the operator has released the start button. However, the motor continues to run only after the card tray 145 has been lowered into the printing position.

In order to tell the operator that the system is ready for a printing operation, a ready lamp 186 is provided. This lamp lights only when the relay is in its actuated condition and contacts 187 are closed. The lamp 186 and contacts 187 are connected in series with a secondary winding 188 ofa transformer whose primary winding 190 is connected to the powerlines in series with main switch 181. Lamp 186 is in parallel with a diode 191 and a capacitor 192, During the operation of the circuit, capacitor 192 is charged to a direct current potential and might discharge through the second indicator lamp 194, except that contacts 193, in series with the capacitor 192 are now open. At the end of the printing cycle, when the relay 173 is again normalized, and contacts 193 are closed, a second lamp 194 is lighted because a series connected silicon-controlled rectifier 195 is maintained conductive by the charge on capacitor 192. As soon as the charge leaks off, the rectifier is made nonconductive and the lamp 194 is extinguished. This second lamp 194 indicates that the printing cycle has been completed.

A third pair of contacts 196 is connected in series with the direct current source of potential 184 and the two lamps 118 and 123 (FIG. 2) mounted adjacent to the rotating wheel 120. As long as the relay is in its operated condition, these lamps remain lighted and provide light flashes for transducers 117 and 124. Contacts 197 send direct current power to the End of Message circuit 61, the operation of which will be described hereinafter. The function of holding contacts 175 have been described above.

INPUT CONTROL CIRCUIT FIG. 1 shows an input control circuit 43 connected to the main amplifier-filter circuit 21. This control circuit senses all the input signals and makes sure that at least two signals of differing frequency have been received and that the signals have the proper intensity and duration. This type of circuit is necessary when the signals are received over a wire line from a distant location. If the signals qualify, the control circuit 43 allows conductor 41 to drop to ground potential from a voltage which is connected to all the AND-circuits 32-1 through 32-18 and enables these circuits to function properly. When the printing signals originate at or near the printing system, the control circuit 43 may be eliminated. A full description of this circuit and its method of operation can be found in application, Ser. No. 806,515 filed Mar. I2, 1969. Since this circuit forms no part of the present invention, it will not be described here.

PRINT CONTROL CIRCUIT The print control circuit 78 is shown in block in FIG. 5 and in detail in FIG. 14. This circuit comprises four transistors 200, 201, 202, and 203. Transistors 200 and 201 are connected in the Darlington manner in order to present a highinput impedance to the input signal which is received over conductor 110. Transistor 202 is for disabling the print circuit so that the print hammer will not be operated during a space operation. In order to accomplish this, the transistor collector and emitter electrodes are bridged across the input terminals of the control circuit. Transistor 202 is normally nonconductive but when a disable signal is received over conductor 77, the transistor is made conductive and absorbs the input signal.

Transistor 203 is a power amplifier having its base electrode connected to the output of the Darlington pair, 200, 201. Its collector electrode is connected to the hammer magnet 80 (FIG. 5) by conductors 113. A 50-volt power supply is connected to the magnet and transistor collector with a capacitor 204 shunted by a diode 205 connected across the power supply lines to absorb the current generated by the collapse of the magnet field when the printing hammer signal is abruptly terminated.

SPACE CONTROL CIRCUIT The space control circuit 206 is shown in block in FIG. 5 and in detail in FIG. 11. The input to this circuit includes two transistors 207 and 208 connected as a Darlington pair for a high-impedance input. The space signal is received over conductor 210 from the print-timing circuit 107 a very short time interval after the print signal is sent to the print control circuit 78.

A power transistor 211 is connected to transistor 208 and its collector electrode is connected over conductor 212 to the space magnet winding 92 to operate armature 93 and the escapement pawl 91. A space operation must be made each time a character is to be printed and each time a space is called for without printing. As described previously a space operation is made by sending a signal through the diode matrix to print a character but, at the same time, sending a hammer inhibit signal to keep the hammer from operating.

At the completion of the space operation, a reset signal is sent from the space circuit 206 over a conductor 213 to reset any or all of the storage multivibrators 44 (FIG. 1) which were triggered at the start of the operation to print a desired character or space the printing assembly. The reset pulse is derived from a transistor 214 coupled to the output transistor 211 by a time delay circuit which includes a capacitor 215 and a series resistor 216. The time delay is quite short, in the order of a millisecond, and is only long enough to insure that the spacing operation is completed before the circuit is normalized.

END OF MESSAGE CIRCUIT The depression of the start button 156, as noted above, activates all the operating circuits to print the desired characters. One of the results of the start operation is the activation and latching of the relay 173 having a winding 174. Another is the start of motor 121 and the sequential activation of the matrix multivibrators 95, 96, 97, and 98. When the message is complete, these operations and others must be terminated and their circuits normalized. The end of the message is signalled by the application of three frequency signals from filter circuits 22-3, 22-7, and 22-9, all applied to triple AND" gate 32-17 (FIG. 1) to send a triggering signal to storage multivibrator 44-17. The output from the multivibrator is sent over two conductors 72 and 75. The first signal, on conductor 72 is sent directly to the end of message circuit 61 shown in block in FIG. 5. The second signal, on conductor 75, is sent through the diode matrix as a print signal and an asterisk is printed on the card in the card tray 145. This operation has been described above.

The first signal on conductor 72 is applied to the base electrode of a transistor 218 (FIG. 10) having its emitter coupled to the firing electrode of a controlled rectifier 220. This rectifier has its anode connected to a common supply conductor 221 which is connected to the positive terminal of battery 184 in series with relay contacts 197. The cathode of rectifier 220 is connected by conductor 222 to EOM magnet winding 168 which operates an armature 166 and pulls two cords 165 and 170. The first cord 165 operates a pawl 163 to trip clutch 162 and pull cord 167 to move the printing assembly base back to its original starting position. The second cord 170 moves the plate 171 to the left and disengage ratchet pawl from all the teeth on rack 146 and permit the card tray to be pulled up by spring 148 to its original starting position. When the card tray reaches its top position, contacts 178 are opened, the relay latching circuit is broken and the relay is normalized. Relay contacts 193, as described previously, are closed and complete a circuit through indicator lamp 194 and controlled rectifier 195 to show a COMPLETE signal on a control panel (not shown). The lamp 194 is lighted for several seconds and then its current is cut off automatically when the capacitor 192 is discharged.

The end of message circuit 61, as shown in FIG. 10 also includes a second controlled rectifier 223 with its anode also connected to conductor 221. The cathode of rectifier 223 is connected to conductor 224 and magnet winding to actuate armature 154 and trigger clutch 151 whenever a NEXT LINE operation is called for. Rectifier 223 is made conductive by a pulse received over conductor 60 and applied to transistor 225. The pulse from this transistor 225 is applied through a coupling capacitor 226 to the firing electrode of rectifier 223.

FIGS. 3 and 4 show the details of two bistable multivibrators, each including two transistors. The storage multivibrator 44 is a simplified design because it is activated by a signal applied to terminal 227, to produce a positive output pulse at terminal 228, then reset by a negative pulse applied to terminal 230. No other action is necessary. The multivibrator shown in FIG. 12 is more complicated because the activating or triggering pulse applied to terminal 114 must transfer conductance from one transistor to the other a number of times during a printing operation. The action must be fast since the transfer of conductance must occur during the time one character on one of the printing wheels is replaced by the next character. In order to speed the action, capacitors 231 and 232 have been added. These capacitors, however, are not large enough to produce a free-running generator. Variations of this circuit can be used for this operation.

One of the storage multivibrators 44-16 (FIG. 1) requires an inhibit pulse during the times either of filter circuits 22-9 and 2240 are producing output voltages. As described above, the inhibit signal is sent by OR"-circuit 70, over conductor 71 to circuit 44-16. Conductor 71 in FIG. 3 illustrates the manner of applying the signal to the storage circuit to maintain it in its normal state.

The OR gate shown in FIG. is used in the circuit shown in FIG. 1 to send pulses from either of two input conductors 233 or 234 to an output conductor 235. This circuit is well known in the art and requires no potential sources for its operation. Diodes 236 block return currents in either input circuit due to currents in the other circuit.

The triple AND gate shown in FIG. 16 is used in gates 3217 and 3248 and is the same as the AND" gate shown in FIG. 12 except that a third input branch has been added. Terminal 237 is for receiving the third negative input pulse which passes through diode 238 to reduce the potential of junction point 38. When all three input terminals receive negative pulses, current can then flow from the output terminal 35 to ground through diodes 40 and 240. A positive voltage applied to conductor 41 inhibits this action.

The general operation of the system will be apparent from the operations of the separate parts as disclosed above. The operator first depresses the start button, starting the motor 121, activating the relay 173, and lowering the card tray into printing position. At this time ready lamp 186 is lighted and the operator can apply signal frequency waves to input terminals -20 or connect these terminals to a line which transmits the signals. As each combination of signals is received, a storage multivibrator 44 sends a positive pulse to one of the horizontal conductors in the matrix and, when the matrix multivibrators apply the desired potentials to the two diodes connected to the selected horizontal conductor, a printing pulse is sent over conductor 106 and the printing hammer is operated to print the desired symbol on a card in tray 145. The use of three printing wheels permits the selection of 45 characters controlled by the first 15 gates, an additional character controlled by gate 32-17, and the follow ing operations (1) space, (2) next line, and (3) end of message.

An alternate form of diode matrix with an alternate means of control is shown in circuit diagrams FIGS. 6 and 8 and cross-sectional view in FIG.-7. The diode matrix includes the same 16 horizontal conductors which are positively biased by a voltage on conductor 112 connected to resistors 113. Only 16 diodes 105 are required in the matrix, each connected between a horizontal conductor and a photosensitive transducer 241 in a scanning array 242. Sixteen transducer circuits are required.

The scanning device 242 comprises a stationary disk 243 secured to a mounting plate 244 and formed with a tumed- 64. As the disk 247 turns light is applied through hole 250 to all the transducers 241 thereby applying a positive pulse to each of the vertical conductors in sequence.

The transducer circuit is shown in FIG. 8. A solid-state photosensitive element 252 is positioned adjacent to each hole 246 and its electrodes are connected to the base and collector of a transistor amplifier 253. A battery 254 is connected to the transistor 253 and to the element 252. A load resistor 255 is connected between the emitter of transistor 253 and the ground terminal. Each emitter electrode of the transistors 253 is connected respectively to a vertical conductor and a diode 105. The transistors 253 are biased by resistors 256 and 257 for nonconduction when no light is incident on the transducer 252. In this condition each vertical conductor is at ground potential. When light is incident on the transducer 252, a positive voltage is generated which is applied to the transistor to make it conductive and send current through resistor 255 to ground. The voltage drop across resistor 255 is then applied to the vertical conductor.

When the diode matrix is operated, all the horizontal conductors are connected to a positive potential by means of conductor 112. As long as no light shines on the transducers, the vertical conductors are at ground potential, thereby removing any potential from the horizontal conductors. The storage multivibrators 44 are normally arranged so as to apply a zero potential to the horizontal conductors.

When one of the storage circuits is triggered to apply a positive potential to its horizontal conductor there is no pulse transfer until the scanning array applies a positive potential to the vertical conductor that is connected to the triggered horizontal conductor. Then, in a timed sequence, a positive pulse is sent through one of the diodes 107 to conductor 106 to the printing control circuit.

Having thus fully described the invention, what is claimed as new and desired to be secured by Letters Patent of the United States, is:

1. An alpha-numeric-printing means for printing symbols on a stationary surface comprising;

a. a splined horizontal rotatable shaft coupled to a motor for turning the shaft at a constant speed;

b. a printing assembly including a central printing wheel and two adjoining printing wheels on either side thereof, said printing wheels mounted on said shaft and movable in an axial direction along the shaft, said printing wheels each having symbols in relief equally spaced on the wheel peripheries;

c. a wheel-shifting means positioned on the printing assembly for laterally moving either one of said adjoining printing wheels into a printing position;

(1. a printing hammer assembly including an electromangetic winding for operating a printing hammer to produce a momentary contact between a recording surface and a relief symbol on one of the wheels, said winding connected to a print control circuit for actuation at a predetermined time during an operating cycle;

. a space control circuit for sending a current pulse to an electromagnet for operating an escapement to move the printing assembly along the shaft a distance of one symbol space at the end of each printing operation;

f. and a printing control circuit coupled between a signalling means and the hammer assembly for sending a current pulse to said winding to operate the hammer and print a symbol.

2. A printing means as claimed in claim 1 wherein said three printing wheels are coupled to a grooved collar and a yoke is engaged by the collar, said yoke coupled to actuating means on the printing assembly for shifting either one of said adj oining printing wheels laterally into a printing position.

tuating the yoke to move the three printing wheels.

6. A printing means as claimed in claim 5 wherein the printing assembly also includes a base plate which supports the print hammer, the print hammer magnet, the yoke, and two magnets for operating the yoke.

7. A printing means as claimed in claim 6 wherein a resilient mechanism is coupled to the yoke and the three printing wheels for returning them to the normal position after each printing operation. 

1. An alpha-numeric-printing means for printing symbols on a stationary surface comprising; a. a splined horizontal rotatable shaft coupled to a motor for turning the shaft at a constant speed; b. a printing assembly including a central printing wheel and two adjoining printing wheels on either side thereof, said printing wheels mounted on said shaft and movable in an axial direction along the shaft, said printing wheels each having symbols in relief equally spaced on the wheel peripheries; c. a wheel-shifting means positioned on the printing assembly for laterally moving either one of said adjoining printing wheels into a printing position; d. a printing hammer assembly including an electromangetic winding for operating a printing hammer to produce a momentary contact between a recording surface and a relief symbol on one of the wheels, said winding connected to a print control circuit for actuation at a predetermined time during an operating cycle; e. a space control circuit for sending a current pulse to an electromagnet for operating an escapement to move the printing assembly along the shaft a distance of one symbol space at the end of each printing operation; f. and a printing control circuit coupled between a signalling means and the hammer assembly for sending a current pulse to said winding to operate the hammer and print a symbol.
 2. A printing means as claimed in claim 1 wherein said three printing wheels are coupled to a grooved collar and a yoke is engaged by the collar, said yoke coupled to actuating means on the printing assembly for shifting either one of said adjoining printing wheels laterally into a printing position.
 3. A printing means as claimed in claim 1 wherein said space control circuit includes an inhibit circuit for disabling the printing hammer assembly when only a space action is desired.
 4. A printing means as claimed in claim 1 wherein the printing assembly operates in synchronism with an apertured wheel secured to the splined shaft and arranged for generating timed signals which are applied to the printing control circuit for printing a symbol.
 5. A printing means as claimed in claim 2 wherein said printing aSsembly includes at least one electromagnet for actuating the yoke to move the three printing wheels.
 6. A printing means as claimed in claim 5 wherein the printing assembly also includes a base plate which supports the print hammer, the print hammer magnet, the yoke, and two magnets for operating the yoke.
 7. A printing means as claimed in claim 6 wherein a resilient mechanism is coupled to the yoke and the three printing wheels for returning them to the normal position after each printing operation. 